High-potential conductor



May 3,-1927.

A. o. AUSTIN" HIGH POTENTIAL CONDUCTOR Filed June 26. 1924 2sheets-sheet 2 f INVENTOR BY L@ ATTORNEYS vso tion.

Patented May .3, 1927.

UNITED STATES PATENT., OFFICEQ Ammon o; AUSTIN, or eliminaron, omo,Assrenon, nr Mestre AssieNMEN'rs, 'ro 'ran 01110 nnAss comenzar, orMANsrrnLn; omo, a ooaroaerron' or new ran- SEY.

l HIGH-remnant connno'ron.

\. i Application led ,Tune 26, '1924. Serial No. 722,442@

This invention relates to conductors for reducing corona losses at highvoltages and has lor its olneet the vprovision of conductors which'shall he mechanically and electricallyV jeliicient and 'l in which thelosses due to corona will he reduced. l

The invention is exemplified in the combination and arrangement of partsshown in the accompanying drawings in the following specification and itis more particularly pointed out in .the appended claims.

ln the drawings- Fig: 1 is an elevation of a'portion of av conductorhaving onefemhodiment of the present invention applied thereon.

Fig-2 is a transverse section .of doctor shown in Fig. 1.

Figs. 3 and 4 are views and 2 `showing 'another form of tion. l

Figs. fand are views similar to Figs. 1 and 2 showing another form oftheiinvention.

Figs. 7 and 8 are views similar to Flgs. 1 and 2 showing yanother formolrtheinvention.

Figs. 9 and 10 are views similar' to Figs. 1

the consimilar to Figs. l

the invenand' 2 showing another jformof the invention. f

Figs. 11 and, 12 are viewssirnilarA to Figs. 1 and 2 showing anotherform of the invention. y f

Figs. 13 and 14 are views similar to Figs. 1 and 2 showing another formofthe invention.

' Figs. ,15 and 16 are views similar to Figs. 1 and 2 showing anotherform of' the invention.

Figs. 17

and 18 are views similar to Figs. 1 and 2 showing another vform of theinven- Intransmission at high voltages the discharge into the air orcorona loss is an important economic factor. Since the amount of powerwhich can he transmitted over a conductor with a given percentage lossincreases as the square of the voltage, it is highly important 'that ahigh voltage be used in order to reduce the size of the conductor andlower the costpoi the transmis-V sion line. For a given amount of power,by increasing voltage, ,the size of the conductor canbe decreased withthe same percentage and described v larger streams; hence,

of loss. It the voltage is high, however, the smallsize conductor mayvdischargevinto the iur and the increased loss odset economic gains inreducing the size of the conductor llVhere very high voltages are used,smooth conductors may operate with corona loss. Under storm conditions,ever, the smooth conductor may have a very small rough lower edge formedhy the drip water running oil of same.. With a smooth conductor, thiswater tends to run oli in much the losses may really he greater and. thedanger oi' arcing" to ground may he materially increased, as against aconductor which has a fairly uniform roughness which will break up thedrip water into small quantities. l

The conductors shown in Figs. 1, 2, 3, e, 13, 14e, 15, .and 16accomplish this result by the main corona pressing strands, whereas theattaching or binding members hold 'l the vcorona pressing stran to themain condpctor tend to accomplish the same result in Figs. 5,6, 7, 8, 9,10, 11, and l2. A small conductor which will brealr' up the drip watermay have lower losses and he less likely to permit an are to, form fromconductor to ground than a very large smooth conductor where the latterpermits a concentration of the drip water at fewer points. l Not onlydoes `the concentration of the drip water from a larger conductor tendto cause discharge or increase the losses but the larger projected areaof the large conductor tends to increase the amount of' drip Water andthe length of the stream falling from the conductor. With a largerradius of curvature, there is also, less tendency to `break up thestream of Adrip water.

properties might be used to advantage.

large v howv .If thesize of the conductor, however, 1s

too small, the losses will be high and the compounds formed by thedischarge will ten to destroy the conductor.

n addition to the installations where the amount of power-transmitted'will hardly warrant a large conductor, there are installations wherethe loss is likely to he very considerable from 'corona discharge, owingto the very highvoltage useda` This loss is greatly increased where thealtitude is high or under storm conditions where the conductor is wet.

lu a. very large conductor, the brush discharge tends to startI abruptlyat some point ou the voltage wave and may cease abruptly. 'lhis tends toset up oscillations which it would be desirable to eliminate. The coronadischarge is due to aJ high electrostatic stress in the air. This stressmay be reduced by increasingl the size ot the conductor or bysubstituting a material which has a higher dielectric vstrength thanair. v

`Where the projected area oli'the conductor is large,.the amount. oiwater intercepted during a rain may be considerable. Even though'the-conductor is quite large, the

water falling ofi' the lower partof the conductor forms an exceedinglysharp edge and tends to increase the loss. 'This tends to oilset thebenefit of the large diameter.

ln very largeconduetors there is also a tendency for the discharge to beless uniform than in the case of the small conductors; hence,`adischarge at any point on the large -conductor may be larger and projectfurther into the air than in the case'of the small conductor. This isdue to the fact that in the small conductor there is a mutual screeningetteet owing to the numerous discharges which re-act upon each other,while in the large conductor the absence to a large extent oit `suchscreening action permits a streamer or discharge to aiect a largerelectrostatic tield. This tends to ott'set the advantage of the largeconductor and it is therefore highly advisable to prevent discharge fromthe larger size of conductor as well as the smaller size of conductor.

lf the entire conductor could be covered with an insulation which shouldhave a greater strength than that of air, the desired result would beobtained. It would be prac,- tically impossible, however, to maintaininsulation of this kind owing to the cost and aging of the same. A verymaterial et'ect, however, may be obtained by providing a few conductorswhich* project beyond the outer layer ot the main conductor and coveringthe projecting conductors with insulation such as insulating enamel,rubber,

guttapercha or other suitable material. `In

order to obtain a material benefit it is not necessary that theinsulation be continuous on the project-ing conductor constituting thecontrol or corona suppressing strands.

ln general, the covering of a conducting surface with insulation withgreater dielectric strength than that of air permits the projection ofthis conductor further into the `electrical field, in order to providea` screening action for suppressing discharges from electrodesorcondncting surfacesI in this vicinity, the inner portion of theinsulated control being connected electrically to the body which it`isdesired to protect.

Figs. l and 2 showone method ol' producing thedcsired result. Theconductor is composed otl a main conductor l similar to that generallyused for transmission work, the one shown in the drawing comprising aplurality of strands. strand 2 having a covering 3 oi dielectricmaterial is wound around this conductor l so as to project outwardlyfrom the surface. The distance between turns ofthe winding 2 may vary inaccordance with the result desired. ln place of a single strand, two ormore strands may be used. These strands may be wound in the samedirection and may contorni to the lay of the cable, or, the individualstrands may be wound in opposite directions to each other. Where atewvstrands only are used twisted around the conductor, these strandsmay be installed by proper equipment even after a cable-is in position.The corona suppressing strand 2 may have little or no insulation on theinner surface 4where it comes in contact with the main conductor. Itmatters littlev whether electrical contact is established at the timethat the strand is puton or not as insulation will be broken down by thecharging current and this will effect goed contact. If a conductingstrand is used, a' drop in potential along the main conductor will alsoinsure contact between the coro of the protecting strands and the mainconductor. It is usually not necessary to make a detinite'metallicContact between the conductor and the core of the corona suppressingstrands for the reasons stated above, although this may be accomplishedin several different ways. It thereis no contact at the time ofinstallation, vibration will tend to maintain a contact surface,particularly it the corona suppressing strands are'wound loosely aboutthe main conductor.`

Figs. 3 and t'show the several corona sup pressing strands or elements,the number 4 designating the cor'o a suppressing strands and 5 thestrands of the main conductor. kThese strands may be wound with the samelay as the main conductor or in opposite directions. If wound in anopposite direction, it is usually advisable to apply varnish or materialwhich will cause the strands to maintain their relative position unlessthey are close together. lVhen wound in a lay corresponding will tend tostay in proper position, although it may be advisable to wrap theconductor with a protecting material until time ot installation.

:Figs 5 and 6 show a similar construction to that in the other tigureswith the excepto that inthe cable they4 diictor 111 must be establishedoccasionally.

lll)

tion that the corona suppressing 'strands 6 may be supported parallelwith the axis ot the main conductor or spiraled around it. The coronasuppressing strands 6 are held to the main conductor strand 7 eitherwholly orpartially by a small wire orbinding strap '8 wound aroundsaine.

This binding member -should preferably be of insulating inaterial7although it may he of metal in .the form ot' a bare wire or membercovered with insulation as in the case of the corona' suppressingstrands-6.' Any 4equivalent .construction such as rings oi stainpingsmay he used for the purpose. If. the corona suppressing strands have ahigh degree o'fiiisiilation they may be located at some distance fromthe conductoras in ll1 igures 7 and 8. vln Figures 7 and 8 theconstruction is somewhat similar to that inl Figures 5 and ,6

except that a single corona suppressing,

strand 9 is used hung-below the conductor. This strand may be spaced-from the conductor and attached to the same mechanically only atyfrequent intervals. This strandy will tend to minimize the dischargetrom- 'drip Water.- In this case 9 is the corona'suppressingstrand, 10isthe main conductor and 11 the mechanical connecting means between thecorona suppressing strand and the main conductor. y

In Figs. 9 and 1.0 two protecting strands 12 are shown so that the dripwater may fall directly 'from the main conductor and not from the coronasuppressing strands. With this arrangement, less insulation is requiredon the corona suppressingv .strands as the drip Water tends to leave themain'conductor strands 13 directly rather than from the coronasuppression strands 12.` The corona suppressing strands`12 arepreferable spaced 'from the main conductor strands 11 by a small strapor holding means 14.

Figs. 11 and 12 show one method ol' attaching to the main conductorwhich will tend to hold the corona suppressing strands 15 at a distancefrom the main conductor. The attaching means 16 may be kin the torni otWater resisting cord or wire or metallic members may also be used, asthey are needed only at intervals suliicient to obtain proper spacinf.Where the attaching member 16 is a poor conductor, electrical contactbetween the core. of the suppressing con- This maybe done by severalturns of Wire 17 or a little metal ring placed about the conductor whichWill come in contact with the inner edge of the corona suppressing`strands 15 and establishcontact.

Where a considerable amount oi protection is desired or very quietoperation is desired, as around bus structures, a construction shown inFigs. 13 and 14 may be used to advantage. In this case the coronasuppressing element 18 is made up in the form of a helix having a. milchlarger diameter than the main conductor 19. The member 18 may be'attached to the main. conductor 19 by another wrapping 2O so as tolreepthe turns of the helix iii'pi'oper position.

The strands of the corona suppressingele- A ments may be made in anumber of diil'erent 'ways without changingtlie principle ot theinvention. One method is to app y a layer ol' material which may beimpregnated with a. varnish or insulating material to increase itsdielectric strengthor to provide Water protection, such as cottonWrapping impregnated with linsced oil or an insulating varnish. Eventhough there' may be some deterioration in time, it is a comparativelyeasy matter to coat the outer-portions of the Y ywill strike from theconductor to ground.

This tends to reduce the danger of grounds on the system. l l

pFigs. 15 and'lG show the conductor made up having corona suppressingstrands 22 having the same lay as the main conductor strands 21. Figs.17 and 18 show a conductor having the -corona suppressing strands 24meshed with the main'conductorvstrands 23. This arrangement tends toprevent the displacement ot the coronasuppressing strands.

'l claim:

1. In an electrical transmission line for high potentials a currentcarrying conductor having 'portions disposed along the lengthythereo andprojecting beyond the main contour of said conductor, said projectingportions loeing electrically connected with the main body of saidconductor and covered with dielectric material to reduce Acorona loss insaid conductor.

2. 1n an electrical transmission line `for high potentials a currentcarrying con ductor having a plurality of periplierally protectinglongitudinally extending ribs,

said ribs having electrical connection with `'said conductor and havingthe outer portion thereof projecting beyond the main contourr on theconductor hut in electrical connection thereivith, the outer portion ofthe projecting `tend to cut down the' coronalosses which iso strandbeing covered with dielectric material. 4. In high lpotentialtransmission lines, a bare. conductor and-a strand of dielectricallycovered material wound upon said.

bare conductor said strand having electrical connection Withsaidconductor.

5. In high potential transmission lines, a bare current carryingconductor and a plurality of strands of dielectrically covered conductormaterial Wound upon and in electrical connection with said bareconductor and arranged in spaced relation about the v.periphery thereof.

, 6. In high potential transmission lines, a conductor comprising aplurality of strands :all in electrical contact,'oue of said strandshaving its Vouter portion arranged to project beyond the contour of theconductor i ARTHUR o. AUSTIN.

